The following property and equipment section was obtained from a recent Abbott Laboratories 10-K. Property and equipment, at cost Land........ Buildings...... Equipment...... Construction in progress. $ 370,949 2,655,356 8,813,517 920,599 12,760,421 6.757,280 $ 6,003,141 Less: accumulated depreciation and amortization.... Net property and equipment... The company also provides the following disclosure relating to the useful lives of its depreciable assets. Property and Equipment Depreciation and amortization are provided on a straight-line basis over the estimated useful lives of the assets. The following table shows estimated useful lives of property and equipment. Classification Buildings...... Equipment.... Estimated Useful Lives 10 to 50 years (average 27 years) 3 to 20 years (average 11 years) During the year, the company reported $868,808 for depreciation expense. What is Abbott Laboratories' estimated useful life of depreciable assets